The document describes a solar power controller (SPC) that can provide constant power to loads even under insufficient solar radiation. The SPC consists of two DC-DC converters connected to a solar panel and storage battery. Maximum power point tracking controllers are used to extract power from the solar panel and control battery charging. Under sufficient radiation, the solar panel powers the load directly. When radiation is insufficient, both converters share the load, drawing additional power from the battery to maintain a constant 125V output. The SPC was tested to drive a 22W load at different radiation levels with 87% efficiency.

1. SOLAR POWER CONTROLLER FOR CONSTANT
POWER LOAD
SEMINAR REPORT
Submitted by,
VAISAKH SHANMUGHAN
in partial fulfillment for the award
of
Bachelor of Technology
in
ELECTRICAL AND ELECTRONICS ENGINEERING
from
MAHATMA GANDHI UNIVERSITY
DEPARTMENT OF ELECTRICAL AND ELECTRONICS
ENGINEERING
RAJIV GANDHI INSTITUTE OF TECHNOLOGY
KOTTAYAM
2013 - 2017

2. CERTIFICATE
This is to certify that the seminar report entitled
SOLAR POWER CONTROLLER FOR
CONSTANT POWER LOAD
is a bonafide record of the work done by
Mr. VAISAKH SHANMUGHAN (Reg. No.:
13013896) under our supervision in partial fulfillment
of the requirements for the award of Degree of Bachelor
of Technology in Electrical and Electronics Engineering
from Mahatma Gandhi University, Kottayam for the
year 2016-2017.
Prof. REJITH R Prof. RADHIKA R
Assistant Professor Assistant Professor
Department of EEE Department of EEE
RIT, Kottayam RIT, Kottayam
Dr. JAYAN M V
Head of Department
Department of EEE
RIT, Kottayam

3. SOLAR POWER CONTROLLER FOR CONSTANT POWER LOAD
RIT, KOTTAYAM EEE DEPARTMENT

4. ACKNOWLEDGEMENT
I would like to extend my sincere gratitude to Prof. REJITH R,
Assistant Professor, Department of Electrical & Electronics
Engineering, Rajiv Gandhi Institute of Technology, Kottayam and
Prof. RADHIKA R, Department of Electrical & Electronics
Engineering, Rajiv Gandhi Institute of Technology, Kottayam for their
constant support, encouragement and guidance which enabled me to
present this seminar and complete the report.
I am thankful to Dr. JAYAN M V, Head of the Department,
Electrical and Electronics Engineering for his kind co-operation.
I would also like to express my gratitude to all my classmates and
friends, without whose endless support and help, I could not have
completed this work in time.
VAISAKH SHANMUGHAN

5. ABSTRACT
A 125V solar power controller (SPC) capable of driving load at
constant power under insufficient solar radiation. The SPC consists of
two DC-DC converters along with MPPT controllers and a storage
battery. One of the DC-DC converters is connected directly to the solar
panel and the other is to the storage battery. To extract the maximum
possible electric power from the solar panel MPPT controller is used.
The converter steps up unregulated solar panel voltage to a regulated
125V at the load end. The output voltage can be adjusted to any
desired level from 20V to 200V DC depending on the application. The
proposed controller can provide constant power at 125V and charge
the battery when photovoltaic generated power is greater than the load
requirements. In contrast, the controller takes additional power from
the battery for driving load at constant power with efficiency of about
87% during insufficient solar radiation. The controller can be
effectively utilized to drive solar powered loads in real time
irrespective of solar radiation

6. TABLE OF CONTENTS
LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
1 INTRODUCTION 1
2 SOLAR POWER CONTROLLER 2
3 CONTROLLER CONFIGURATION 3
4 CONTROLLER OPERATION 5
5 PERFORMANCE OF THE SPC 7
6 CONCLUSION 8
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7. SOLAR POWER CONTROLLER FOR CONSTANT POWER LOAD
LIST OF FIGURES
2.1 BASIC BLOCK DIAGRAM OF SPC. . . . . . . . . . . . . . . . . . . 2
3.1 CIRCUIT DIAGRAM OF DC-DC CONVERTER. . . . . . . . . . . . 3
4.1 MODES OF OPERATION. . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1 OPERATION CHARACTERISTICS. . . . . . . . . . . . . . . . . . . 7
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8. SOLAR POWER CONTROLLER FOR CONSTANT POWER LOAD
LIST OF TABLES
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9. SOLAR POWER CONTROLLER FOR CONSTANT POWER LOAD
CHAPTER 1
INTRODUCTION
The demand of electrical energy is increasing tremendously and about 92every part
of the world. Continuous use of fossil fuels has severe environmental issues due to
global warming . Solar energy, on the other hand, is renewable, environmentally
friendly, and unlimited clean source of energy. It is expected that the effective
utilization of solar energy can fulfil present and future demand of electric energy.
A photovoltaic (PV) module utilizes intensity of sunlight and converts optical
energy into electrical energy. However, the output power of a PV module is not
constant, rather, it varies with the variation of intensity of sunlight due to
environmental conditions as well as man-made shading. To utilize the PV power
completely, it is desirable to use high efficiency power conditioning unit for PV
systems. It is well known that the performance of solar powered loads like solar
driven water pumps (SDWP), solar powered rice mills (SPRM), solar powered
electric vehicles (SPEV), etc. may degrade due to insufficient solar radiation. In
previous studies driving loads at constant power under insufficient solar radiation
were not addressed in details for battery less PV systems. It is therefore very much
important to develop solar power controller (SPC) for driving loads efficiently
under insufficient solar radiation. In this paper a power electronics based 125V
SPC is proposed, designed, and practically implemented. The performance of the
SPC is tested for different solar radiations. The results presented in the present
study demonstrate that the proposed SPC is capable of driving loads at constant
power with 87
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10. SOLAR POWER CONTROLLER FOR CONSTANT POWER LOAD
CHAPTER 2
SOLAR POWER CONTROLLER
Maintaining constant power at the load end for battery less applications, such as,
SPEV, SDWP, SPRM, etc. is the main difficulty in PV systems. Here, a SPC is
proposed that can provide constant power at the load end even when solar radiation
is insufficient.
Figure 2.1: BASIC BLOCK DIAGRAM OF SPC.
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11. SOLAR POWER CONTROLLER FOR CONSTANT POWER LOAD
CHAPTER 3
CONTROLLER CONFIGURATION
The proposed SPC consists of two DC-DC converters (boost converter) along with
MPPT controllers and a storage battery. Two DC-DC converters operate parallel and
share a load in order to maintain constant power at the load end. The block diagram
of the proposed SPC is shown in Fig.2.1. The arrows, as shown in Fig. 2.1 indicate
the direction of power flow. Converter-1 acts as main source and converter-2 acts
as backup source. Converter-1 is connected to the output of an MPPT controller
which is connected to a solar panel and converter-2 is connected directly to the
terminal of a backup battery. The battery is connected to the solar panel via a
MPPT charge controller. The MPPT charge controller protects the backup battery
from over-charging and over discharging.
Figure 3.1: CIRCUIT DIAGRAM OF DC-DC CONVERTER.
Lead acid battery can be used due to low cost and maintenance. Both of the
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12. SOLAR POWER CONTROLLER FOR CONSTANT POWER LOAD
DC-DC converters are designed for 125V DC applications. A control system is
included to adjust the SPC output voltage to any desired value. The main hardware
components of the SPC are ferrite core transformer (ETD-39), current mode PWM
controller (UC3843), ultrafastdiode (UF-5408), resistors, capacitors etc. The most
important part of the proposed solar controller is the DC-DC converters, which
steps up the PV module terminal voltage and give regulated 125V DC at the output
to drive the load. The voltage stepping up capability and efficiency of the DC-DC
converters determines the effectiveness of the proposed SPC. The DC-DC
converters are designed using fly-back converter topology, because it requires
relatively less components and has better efficiency. A simplified circuit-diagram
of a fly-back DC-DC converter is shown in Fig. 3.1. The proposed SPC are
designed to provide 125V DC at the load end, which reduces transmission loss and
enables long distance transmission of power for solar systems.
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13. SOLAR POWER CONTROLLER FOR CONSTANT POWER LOAD
CHAPTER 4
CONTROLLER OPERATION
The controller provides regulated 125V DC terminal voltage at the load end even
under insufficient solar radiation. In the proposed SPC, PV module acts as primary
source and storage battery is a backup source. The major operation of the proposed
SPC are as follows:
Figure 4.1: MODES OF OPERATION.
When PV module power generation is higher than load requirements converter-
1 remains in operation and drives the load connected to it. Converter-2 remains in
idle. The excess PV generated energy is stored in the battery. The charge controller
controls charging and discharging operation of the battery.
When PV module power generation is equal to load requirements converter-1
remains in operation and drives the load connected to it. Converter-2 remains in
idle.
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14. SOLAR POWER CONTROLLER FOR CONSTANT POWER LOAD
When PV module power generation is lower than the load requirements,
converter-1 and converter-2 remain in operation and share the connected load. In
this stage the excess energy stored previously in the battery starts discharging.
When PV module power generation is null, converter-2 remains in operation
and drives the connected load. The excess energy previously stored in the battery
starts discharging in this stage and converter-1 remains in idle.
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15. SOLAR POWER CONTROLLER FOR CONSTANT POWER LOAD
CHAPTER 5
PERFORMANCE OF THE SPC
Figure 5.1: OPERATION CHARACTERISTICS.
Both the Primary Source as well as Secondary Source will contribute to the load.
Initially Battery will be in a fully charged condition,Hence the load is Run by this
secondary source. As the Solar Power builds up across the system, The contribution
of secondary source diminishes.At Optimum power of solar, The system is entirely
run by this primary source alone. The Lead-acid battery starts charging when the
solar power is greater than the optimum value. This switching of source is entirely
controlled by MPPT and DC-DC converters.
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16. SOLAR POWER CONTROLLER FOR CONSTANT POWER LOAD
CHAPTER 6
CONCLUSION
A SPC-Solar Power Controller is used to drive a load at rated power even under
insufficient solar radiation. The controller boosts up unregulated solar panel
terminal voltage to a regulated 125V at the load side. MPPT controllers are used to
obtain maximum available power from the solar panel and to control charging
operation of battery. MPPT charge controllers also protects the battery from over
charge and over discharge. The controller is capable to switch over the battery
from charging to discharging mode depending on the availability of solar radiation.
The effectiveness of the controller is tested for 22W load at different solar
radiations. It is found that the proposed controller provides constant power at the
load side with almost constant efficiency of about 87
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17. REFERENCES
[1] Davide Brunelli, Clemens Moser and Lothar Thiele, Member IEEE, “Design of
a SolarHarvesting Circuit for Battery less Embedded Systems”. IEEE Trans. on
Circuits and Systems, vol. 56, 11 Nov. 2009.
[2] H. Dehbonei, S. R. Lee, and H. Nehrir,“Direct energy transfer for high efficiency
photovoltaic energy systems. Part I: Concepts and hypothesis,”IEEE Trans. Aerosp.
Electron. Syst., vol. 45, no. 1, pp. 31– 45, Jan. 2009.
[3] T. Esram and P. Chapman, “Comparison of PV array maximum power point
tracking techniques,” IEEE Trans. Energy Convers. vol. 22, no. 2, pp.439-449, June
2007.
[4] S. Zhong Yi He, Hong Chen, “Integrated solar controller for solar powered off-grid
lighting system”, Elsevier, Energy Procedia 12, pp. 570-577, September 2011.